Michigan Department of Natural Resources
Fisheries Research Report No.1820, 1975
Reaction of Nearby Lake Michigan Fish Stocks to a Heated Discharge at the Palisades Site
Mercer H. Patriarche
Abstract.-Fisheries surveys were conducted in Lake Michigan in the vicinity of the Palisades Nuclear Power Plant in 1968-1973. While the plant was in operation in 1972 and 1973, comparative sampling of fish within and outside the plume was accomplished five times (more comparisons were not possible because the plant was shut down so frequently). Forty species of fish were captured near the plant. Carp and alewife concentrated near the discharge outlet but elsewhere it appeared that several species were repelled to some extent and a few others attracted to the warm water. For the two predominant species in -the gill nets (perch and alewife), a paired ''t'' test showed no statistical difference in abundance before and after plant operation. There was a 37% drop in mean catch of perch after the plant "came on line, " but variability in the catches precluded any change under 50% from being termed significant. Likewise, no statistical difference in the catch of perch, alewife, longnose sucker, or white sucker could be detected whether the nets were in the plume or outside of it. Plume temperatures were mostly 4-8° F higher than ambient in 1972; and they were 10-15° higher in 1973 when the plant operated at 100% capacity. No significant difference in the seine-haul catch of longnose dace and trout-perch before and after plant operation could be demonstrated, despite pronounced drops in average catches of these fish in the last 2 years. There was a significant increase in spottail shiner in the last 2 years, however. The seining area was 3/4 mile north of the discharge point.Growth and mortality of perch are discussed. It appears that their spawning -time in 1973 was advanced about 3-4 weeks, presumably because of the warm effluent. An estimated 80% of the 2-year-old females and 96% of the 3-year-olds were mature.